<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .yuanxing {
            width: 200px;
            height: 200px;
            background-color: pink;
            /* 圆形直接设置圆角边框的一半 */
            /* 也可以设置 border-radius: 50%; 下同*/
            border-radius: 100px;
        }

        .juxing {
            width: 200px;
            height: 100px;
            background-color: skyblue;
            /* 圆角矩形设置为高的一半 */
            border-radius: 50px;
        }

        .other {
            width: 220px;
            height: 150px;
            background-color: #0af1a8;
            /* 顺时针改变 */
            border-radius: 20px 30px 40px 50px;
        }

        .duijiao {
            width: 250px;
            height: 150px;
            background-color: peachpuff;
            /* 两个值的话改对角 */
            border-radius: 20px 50px;
        }

        .alone {
            width: 200px;
            height: 180px;
            background-color: powderblue;
            border-top-right-radius: 50px;
            /* 其他三种设置 */
            /* border-top-left-radius
            border-bottom-left-radius
            border-bottom-right-radius */
        }
    </style>
</head>

<body>
    1.正方形变圆形
    <div class="yuanxing"></div>
    2.矩形四角变圆
    <div class="juxing"></div>
    3.四个角变不同的角
    <div class="other"></div>
    4.对角相同
    <div class="duijiao"></div>
    5.单变一个角
    <div class="alone"></div>
</body>

</html>